1. Field of the Invention
The present invention is directed to rights expression processing systems and methods for processing rights expressions. In particular, the present invention is directed to an extensible grammar based rights expression system and method to allow processing of new rights expressions.
2. Discussion of the Related Art
Digital distribution of content by content owners over the Internet is a way to reach out to a potentially large market of Internet users. However, such digital distribution comes with a risk of illegal, or otherwise unauthorized, distribution of the content. Rights Management helps reduce this risk thereby enabling content owners to protect and profit from their digital content. A Rights Management System is utilized to specify the usage rights for content, or other things and to enforce the usage rights. The term “content” is used broadly herein and includes digital works such as music, audio files, text files, books, reports, video, multimedia, pictures, executable code, or any combination thereof.
Various implementations of Rights Management Systems and rights associated with digital content are known as disclosed by U.S. Pat. No. 5,629,980, U.S. Pat. No. 5,634,012, U.S. Pat. No. 5,638,443, and U.S. Pat. No. 5,715,403. Hence, the details of Rights Management Systems are not discussed specifically herein. As evident from these references, a Rights Management system can take many forms, and can employ varying levels of complexity depending on the security required, the nature of the thing being managed, the complexity of associated rights and conditions, volume and other factors.
FIG. 12 illustrates an example Rights Management system 500 and the associated workflow that can be used to distribute digital content. Typically, when a user goes through an activation process, information is exchanged between activation server 502 and client application 506, and is downloaded and installed in client application 506. Client application 506 serves as a tamper resistant security component and contains the set of public and private keys 504 that are issued by activation server 502 as well as other components such as any necessary engine for parsing or rendering protected content 508.
The Rights Management system 500 also includes a content preparation application 503 that protects clear content 501 through encryption or other protective mechanism to thereby provide protected content 508. The content preparation application 503 also specifies usage rights in a rights label 510 that is associated with protected content 508. The rights label 510 and specifies usage rights that are available to an end-user when corresponding conditions are satisfied. A rights expression language (herein after “REL”) such as XrML™ may be used to specify the rights and conditions set forth in the rights label 510. The rights label 510 and the appropriate encryption key that was used to encrypt the clear content 501 is then provided to the license server 512.
The license server 512 manages the encryption keys and issues license 514 that allows exercise of usage rights. For example, rights label 510 may include usage rights for viewing protected content 508 upon payment of a fee of five dollars, and viewing or printing protected content 508 upon payment of a fee of ten dollars. Client application 506 interprets and enforces the usage rights that have been specified in license 514 to provide clear content 516 that may be used by the end user.
The components and modules of the Rights Management system 500 can be located in one or more than one device. For example, the activation server 502 and the license server 512 could be the same server or other device, or plural separate devices. The protected content 508 may be any type of content including a document, image, audio file, video file, etc. Further details of Rights Management systems are set forth in further detail in the references noted above, and consequently, are not discussed specifically herein.
Thus, Rights Management systems not only protect content, but also enable content owners to manage the sale and use of their content by means of licenses. Licenses include rights expressions to articulate usage rights and to associate usage rights to a content. Licenses may be specified for different stages during the life cycle of digital content. For example, when digital content is released to a distributor, licenses may be specified by content owners to limit distribution of the digital content to a particular region or a period of time, or to restrict how content may be repackaged. Of course, licenses themselves must be protected as well since they are a controlling facet determinative of how content is used. In this regard, licenses are typically digitally signed by the issuers so that their integrity and authenticity may be verified before being interpreted.
A license typically includes a grant element, a principal element, a right element, a resource element, and optionally, a condition element. In particular, a license contains one or more grant elements which defines the details of the usage rights granted. The one or more grant elements may specify a principal element, a rights element, a resource element and, optionally, a condition element. The principal element identifies a principal (user) or a group of principals who is/are granted the right to access or use the protected resources, while the rights element names a specific right (e.g. play, view, print, copy) to be given to the principal with regards to accessing or using the protected resources. The resource element specifies the protected resources, and the optional condition element specifies any conditions that are imposed on the right to use the protected resource.
A license is typically embodied as a rights expression. A rights expression is a syntactically and semantically correct language construct, based on a defined grammar, to convey rights information. As noted, an example of a rights expression language is XrML™. It is important to note that the term “rights expression” as used herein is not be limited to licenses in particular, but refers to any expressions that may be used by the Rights Management system to convey information. Thus, the term “rights expression” and derivatives thereof as used herein generally refers to expression of licenses, license components and/or fragments (such as the grant element, principal element, right element, resource element, and/or condition element), as well as any other appropriate expressions. Moreover, rights expressions may be in a variety of different forms ranging from binary encoded sequences that target resource constrained applications, to multi-level REL construct that describes complex rights information for managed distribution of digital resources and rights granting paradigms.